JP2012507039A - Security device with printed metal layer in the form of a pattern and method of manufacturing the same - Google Patents

Abstract

  A transparent base layer (14) having a surface (16) provided with an optically variable relief microstructure, and a transparent high refractive index layer (18) adapted to the surface relief microstructure on the surface of the base layer (14) And a reflective metal layer (20) printed on the bright high refractive index layer. The metal layer (20) is printed in the form of a pattern. The thickness of the transparent high refractive index layer (18) is selected to achieve constructive interference of light at a wavelength λ in the range of 450 to 650 nm reflected from each surface of the transparent high refractive index layer.

Description

  The present invention relates to a security device and a manufacturing method thereof.

  In particular, the present invention relates to a security device in the form of holograms and / or DOVIDS (Diffractive Optically Variable Identification Devices) that can be widely applied to articles and high-value certificates.

  In previous security devices of this type, a base layer such as lacquer or resin is provided with an optically variable relief microstructure, on which a metal layer is applied to improve the device's reflective properties. Vacuum-deposited. This metal layer is selectively demetalized, such as by etching, to allow information to be visualized when the device is attached to an article or certificate. Previous security devices of this type are relatively expensive to manufacture due to the complexity of metal vacuum deposition and selective etching. International publication WO 2005/049745 describes an improvement in which a platelet or strip of metal ink is printed as a reflective layer on a surface relief microstructure. This is also described in International Publication WO 2005/051675 and US Pat. No. 5,549,774.

  The use of a printed metal layer instead of a vacuum-deposited layer is a simpler and cheaper way of providing a reflection enhancing layer, in the design of security devices by selectively depositing metal in some areas. Provides benefits such as increased flexibility. In addition, special additives can be added to the metal ink mixture (as described in WO 2005/049745), thereby changing the chemical and / or physical properties. By introducing transparent organic pigments and / or solvent-soluble dyes into the ink, a multicolor effect can be realized, and colored shadows can be realized.

  However, such diffractive and holographic devices have a lower reflectivity from the surface of the metal ink in the form of platelets or pieces compared to the reflectivity from the surface of the vacuum deposited metal layer. Exhibit relatively poor diffractive structure regeneration. This degradation is due, in part, to the fact that metal platelets or small pieces of float are formed in the ink-reflective resin binder. Since metal platelets or pieces are generally composed of less than 25% of the volume of ink, the reflectivity is essentially lower than that of a continuous metal film. If the metal platelet or piece constitutes 25% of the ink volume, the reflectivity is at most close to 25% of the continuous vacuum deposited metal film. In particular, plate-like metal platelets are comparable to vacuum-deposited coatings in diffractive or holographic surface relief microstructures, albeit superior to conventional metal pieces or pigments. Can not fit closely. In particular, the fine part of the relief structure in contact with the binder does not contribute significantly to the diffracted wavefront because of the similarity in the embossed layer and the refractive index of the binder (n = 1.45 to 1.5). This is because the refractive index basically matches. In addition, there is a statistical spread in the alignment of the platelets or pieces, which further spreads the diffracted light, resulting in a decrease in brightness and gloss of the diffractive or holographic image.

  International Publication No. WO 2005/049745 attempts to improve the efficiency of such a device by ensuring that the pigment to binder ratio is sufficiently accurate to allow the pigment particles to align with the grating outline. It is described. However, the results of trials with actual diffraction gratings are not as bright as observed with vacuum deposited metal layers.

  JP 2008-139713 describes a hologram transfer foil (foil) made of a carrier layer and a release (release) layer, on which a hologram layer, a reflection such as titanium oxide, is provided. A layer, a high-brightness ink layer comprising a metal vapor deposited film piece surface that is treated with organic fatty acids or the like and optionally printed, and an adhesive layer are provided. The purpose of this structure is to prevent corrosion of the metal in the high brightness ink layer. This document does not discuss the above-mentioned problems associated with the use of platelet or strip metal inks, and the reflection is sufficiently thin to fit the surface relief of high brightness metal and hologram layers. It also does not discuss the boundary effect between the strata.

  According to a first aspect of the present invention, a security device includes a transparent base layer having a surface provided with an optically variable relief microstructure, and a transparent height adapted to the surface relief microstructure on the surface of the base layer. And a reflective metal layer printed on the transparent high refractive index layer, the metal layer is printed in the form of a pattern, and the thickness of the transparent high refractive index layer is determined by each surface of the transparent high refractive index layer. Is selected to achieve constructive interference of light at a wavelength λ in the range of 450 to 650 nm reflected by.

  According to a second aspect of the present invention, a method of manufacturing a security device provides a transparent base layer having a surface with an optically variable relief microstructure, and a surface relief microstructure on the surface of the base layer. To provide a transparent high refractive index layer, to provide a reflective metal layer on the transparent high refractive index layer, the metal layer is printed in the form of a pattern, the thickness of the transparent high refractive index layer is It is characterized in that it is selected to achieve constructive interference of light at a wavelength λ in the range of 450 to 650 nm reflected from each surface of the refractive index layer.

  The present invention solves the above-mentioned problem, particularly the problem related to Japanese Patent Application Laid-Open No. 2008-139713, by enabling the metal ink pattern to be printed without a large loss of brightness. It is important for the inventor to examine the printed metal pattern to improve the light reflected from the area where the metal is printed, which includes the rays reflected from the metal / high index layer interface. Constructive interference occurs with light rays reflected from other surfaces of the high refractive index layer, and destructive between light rays reflected from opposing surfaces of the high refractive index layer where the metal is not aligned. This is done by ensuring that interference occurs. Thus, this not only improves the brightness of the light reflected from the metal part, but also reduces the reproduction of the hologram in other parts, thereby further improving the visibility of the printed metal pattern.

  Here, a high refractive index means that the refractive index exceeds the refractive index of a transparent, typically embossed base layer by 0.5 or more. Since the refractive index of the base layer is typically in the range of 1.45 to 1.55, the high refractive index material has a refractive index of 2.0 or higher. Indeed, high refractive index materials with good visual transparency have a refractive index in the range of 2.0 to 2.5.

  The optimal brightness carefully adjusts the thickness of the high index layer to ensure constructive interference between the two partial amplitudes diffracted from the first and second surfaces of the high index layer. It can be realized by determining. The first surface is a boundary that forms interference with the surface relief microstructure, and the second surface is a boundary that forms interference with the metal layer. The thickness of the high refractive index layer necessary to ensure constructive interference between partial diffraction amplitudes is constructive interference between the partial amplitudes reflected at two strictly planar boundaries. Unlike the thickness required to do this, it is best to determine empirically by actual methods, because the exact value is the periodicity and amplitude present in the optically variable microstructure, This is because it depends on the incident wavelength.

  In order to achieve destructive interference in the absence of metal, the non-metallic region of the second surface of the refractive index layer should contact the low refractive index body. This body is typically an adhesive, but may be air.

  An optically variable relief microstructure can be realized in conventional shapes and typically has a diffraction grating or hologram. However, combinations of these are also possible. The holographic generation structure may be any structure that generates a graphic image by a light diffraction mechanism. Such holographic generation structures include, but are not limited to, those formed by technology lists such as optical interference, dot matrix interference, lithographic interference, or electron beam interference.

  The base layer can also be made of conventional materials and is typically made of lacquer or resin. The optically variable relief microstructure is formed by embossing or casting / curing the surface of the base layer.

Typical examples of materials suitable for the transparent high refractive index layer include one of zinc sulfide (ZnS), titanium dioxide (TiO ₂ ) and zirconium dioxide (ZrO ₂ ).

  The metal layer can be formed using any of the techniques and materials detailed in WO2005 / 049745A, which is incorporated as referenced in this application.

  Typically, the metal layer is formed from one or more inks containing suitable metal particles such as platelets, strips or pleats (lamellas) and a binder.

  The metal particles may be from metals such as aluminum, copper, zinc, nickel, chromium, gold, silver, platinum, or other metals, or related alloys such as copper-aluminum, copper-zinc or nickel-chromium. Selected and vacuum deposited.

  Organic colorants or pigments may be added to the binder to achieve the desired color.

  Although not essential to the present invention, the metal particles are naturally highly platelets or pleats, i.e., the size of the metal particles (platelet length) along an axis parallel to the reflective boundary crosses the reflective boundary. It is desirable that it is sufficiently larger than the dimension (small plate thickness) in the direction. Here, “sufficiently large” means that the platelet length is at least 2 to 5 times the platelet thickness and desirably more. The platelet thickness depends on the basic method of manufacture and is in the range of 10 nm to 100 nm, but for application to holographic or diffractive structures, preferred thicknesses are in the range of 15 nm to 100 nm, in particular in the range of 25 nm to 50 nm. It is. It is important to ensure that the piece conforms to the shape of the optical microstructure relief with a spatial sufficiency factor, which means that both the length and width dimensions of the platelet are optically variable. It can be realized by selecting so as to exceed a certain period in the diffraction fine structure.

  Consider an ink having a structure in which pieces of aluminum having a length and width of about 1000 nm (thickness of 25 nm) are dispersed. As the ink dries, the metal pieces make very irregular contact with the grating surface relief, but the period of the gap between the pieces is reduced by a factor of 10 compared to a piece with a length and width of 100 nm. This greatly reduces scattering. Furthermore, the fact that the average length and width of the pieces is 40 times the thickness is not mechanically strong enough to allow the pieces to stand under the influence of compressive forces caused by gravity and dispersion upon drying or hardening. Means that. For this reason, as the ink dries, the pieces tend to easily conform to the shape of the lattice relief. This improves the fit to the shape of the grating profile and allows each individual piece to straddle one grating groove without interruption, exhibiting higher diffraction efficiency than the 100 nm piece. Further improvement in diffraction efficiency can be achieved by further increasing the length and width of the platelet. In particular, if you consider each grating groove as a chain of coherent secondary sources or a single secondary source of obstructions in a row (ie, a grating row), from basic diffraction theory, the maximum diffraction efficiency Is not achieved up to 8-10 or more uninterrupted rows of coherent secondary light sources, i.e. reflective grating grooves. Thus, in the illustrated scenario, the platelet pieces have a length and width sufficient to straddle at least 8-10 diffraction grating grooves. Thereby, for a typical DOVID, a particularly preferred platelet length and width is on the order of 10,000 nm or more.

  Binders are nitrocellulose, ethylcellulose, cellulose acetate, cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), alcohol soluble propionate (ASP), vinyl chloride, vinyl acetate copolymer, vinyl acetate, vinyl, acrylic, polyurethane , Polyamide, ester gum, hydrocarbon, aldehyde, ketone, urethane, polyethylene terephthalate, terpene phenol, polyolefin, silicon, cellulose, polyamide, and any one or more selected from the group comprising ester gum resins.

  Preferably, the binder has 50% nitrocellulose and 50% polyurethane.

  The mixture may additionally have a solvent. The solvent may be an ester / alcohol mixture, and is preferably a normal mixture of propanol and ethanol. More preferably, the ester / alcohol mixture is in a ratio between 10: 1 and 40: 1, more preferably between 20: 1 and 30: 1.

  Solvents used in metal inks are esters such as n-propyl acetate, isopropyl acetate, ethyl acetate, butyl acetate; ethyl alcohol, industrial methylmethanol-modified alcohols, isopropyl alcohol, or alcohols such as normal propyl alcohol; One or more of a ketone such as methyl ethyl ketone or acetone; an aromatic hydrocarbon such as toluene; or water.

  The metal layer is typically applied to the high refractive index layer by conventional gravure, rotogravure, flexographic, lithographic, offset, letterpress, stencil and / or screen printing, or other printing processes.

  In one approach, the metal layer is printed in the form of a security pattern (a region or region having a shape), the pattern being arranged in a pattern generated by an optically variable relief microstructure. The metal pattern can at least partially constitute an area of a genuine security pattern work, for example, a security pattern in the form of a fill-gree effect with a minimum size of about 50 μm. Such genuine patterning of metal is beyond the range that counterfeiters can reproduce or approximate with hot stamping technology using colored decorative foils.

  In some cases, the metal layer can be formed of a single ink so as to provide the same color across the entire area of the security device. It can also be set as a vacuum-deposited metal layer by the same method. However, changing the color across the device or between different regions of the device can also be achieved by using different colored metal inks. Different colors can be created in metal inks by adding different colorants (pigments) to current binders, or by using metal platelets or particles made from different metal species (eg, copper and aluminum). , Or a combination of both. The platelets or pieces can be composed of multiple optical thin films, and their color is derived from the iridescence of the thin film.

  Security devices can be used in a wide variety of applications known to those skilled in the art. Typically, the security device is attached to an article like a security member. Examples of such security components are banknotes, checks, traveler checks, certificates, revenue stamps, electronic payment cards (credit cards, debit cards), identification cards and certificates, driver's licenses, passports, brand protection or authenticity Contains a label or stamp.

  Several examples of security devices and methods according to the present invention will be described with reference to the accompanying drawings.

FIG. 1A shows a schematic cross-sectional view of the apparatus of the first embodiment. FIG. 1B shows a plan view of the apparatus of the first embodiment. FIG. 1C shows a cross-sectional view of the apparatus of the second embodiment. FIG. 1D shows a plan view of the apparatus of the third embodiment. FIG. 2A shows a plan view of the apparatus of the fourth embodiment. FIG. 2B shows a cross-sectional view of the apparatus of the fourth embodiment. FIG. 2C shows a plan view of the device of the fifth embodiment. FIG. 2D shows a cross-sectional view of the device of the fifth embodiment. FIG. 3A is a view similar to FIG. 2A but of the third embodiment. FIG. 3B is a view similar to FIG. 2B but of the third embodiment.

  The apparatus shown in FIG. 1A has a PET carrier layer 10 of the conventional type. The surface 12 of the carrier layer 10 is coated with a lacquer layer 14. In another example (not shown), a release (release) layer can be provided between layers 10 and 14, and in yet another example, layer 10 is transparent and remains secured to layer 14 Used in.

  The lacquer layer 14 is embossed on its surface 16 with an optically variable relief microstructure that defines a hologram or diffraction grating.

  The optically variable relief microstructure is coated with a transparent high refractive index (HRI) layer 18 such as ZnS. The HRI layer is typically applied by vacuum deposition using thermal evaporation or sputtering techniques. The HRI layer 18 is thin enough to fit into the relief microstructure 16 where both surfaces 18A and 18B are optically variable. Next, a metal ink platelet or strip layer 20 is printed on the layer 18 in the form of a security pattern, and then an adhesive coat layer or a plurality of coat layers 21 is applied to the metal ink. An example of a suitable metal ink comprises 1000 nm long and 25 nm thick metal strips in a 50% nitrocellulose and 50% polyurethane binder. The platelets fit in contact with the surface relief microstructure of surface 18B.

Normal thickness and coat weight PET (10) is 10-50 micrometers ([mu] m), in particular 15-23 [mu] m.
The embossed lacquer (14) is 0.5 to 10 gsm, in particular 1 to 5 gsm.
Metal ink is in the range of 1-10 gsm, especially in the range of 2-5 gsm.
The weight of the adhesive coat layer is 1 to 10 gsm, particularly 1 to 7 gsm.

  Next, consider the thickness of the HRI layer 18 necessary to generate structural interference between the first and second partial amplitudes. As previously mentioned, mathematically determining the optimal thickness of the HRI layer is quite complex in principle, mainly because different points in the incident wavefront travel at different distances through the HRI layer. This variation increases as the grating structure amplitude increases or as its periodicity decreases.

  However, the principle is that of constructive interference (partial amplitude) between the rays reflected from the two interfaces of the HRI layer formed between two planar (ie optically smooth) layers. The principle remains. In FIG. 1A, consider the reflected rays or partial amplitudes (1 and 2) from the first and second interfaces. Even so, the result does not change, but since the reflected light is considered and the diffracted light is not considered, the grating relief is allowed to have an intensity order smaller than the wavelength of the incident light. Then, compared with the light beam 1, the light beam 2 travels by an additional optical path difference (OPD) 2 nt cos θ passing through the HRI layer.

  Here, t is the thickness of the thin film 18, n is the refractive index of the HRI layer, and θ is the incident / reflection angle with respect to the direction perpendicular to the substrate.

  If the platelet ink 20 has a higher refractive index than the HRI layer, and the HRI layer has a higher refractive index than the embossed lacquer layer 14, half-wavelength (ie, 180 degrees) at both the first and second interfaces. There is a phase shift. Thus, the phase difference between the first and second rays (ie, the first and second partial amplitudes) is determined only by the OPD.

  Thus, there is a constructive interference condition 2nt cos θ = pλ that the OPD should be equal to an integer (P) multiple of the wavelength.

  Alternatively, the term of t is rearranged so that t = pλ / 2n cos θ.

  Here, λ is the wavelength of the target light, and p is a positive integer.

  Simplify by considering the minimum order of interference corresponding to p = 1, and assume a normal incidence angle such as θ = 0 and cos θ = 1.

  In this case, t = λ / 2n, that is, half of the optical wavelength thickness. If the value of 550 nm (the center of the visible spectrum) for λ is assumed to be 2.0 for n, the value of t is approximately 140 nm.

  Similarly, the condition for destructive interference is that OPD is equal to an odd value of a half wavelength, and 2nt cos θ = (2p + 1) λ / 2.

  Alternatively, the term of t is rearranged so that t = (2p + 1) λ / 4n cos θ.

  In this scenario, the minimum order of destructive interference corresponds to p = 0, which would assume normal incidence, and the minimum thickness of the HRI layer required to produce destructive interference is t = λ / 4n It is.

Consider the case of constructive interference t = λ / 2n of interest. Here, the intensity (ie, brightness) of light having amplitudes (A ₁ and A ₂ ) reflected at the two boundaries is proportional to the sum of the squares of the partial amplitudes. More simply,
Brightness = (A ₁ + eA ₂ ) ²
Here, e is a factor that defines the relative phase of the partial amplitude. For constructive interference, e = 1, so
Brightness = A ₁ ² + A ₂ ² + 2A ₁ A ₂
It becomes.

Note that in general, the first partial amplitude is a relatively small fraction (ie, approximately 12-14%) of the incident amplitude. In this case, the brightness of the light reflected by no HRI layer platelets is about A ₂ ^2.

For this reason, the presence of the HRI layer increases the perceived brightness of the platelet ink by the value of the term A ₁ ² + 2A ₁ A ₂ .

Assuming further that A ₁ and A ₂ are approximately equal, ie A ₁ ≈A ₂ , the ratio of the brightness of the reflective structure with the HRI layer to the brightness without the HRI layer (18) is 4A ₂ ² / A ₂ ² = 4. In other words, the effect of the HRI layer (having an optimized thickness for constructive interference) for this special case increases the effective brightness of the platelet ink by a factor of four.

  Considering the effect of the HRI layer (18) on the diffracted light, it is recognized that the analysis of OPD passing through the HRI layer of the diffracted light (2b) is more complicated, but the same principle applies. If the diffracted rays (2a and 2b) constructively interfere in substantially the same phase, resulting in a large increase in the perceived brightness of the diffracted image, if the platelet ink is coated directly onto the diffractive surface relief There is an optimum thickness of the HRI layer that would exceed the brightness achieved. The optimal HRI layer thickness required to achieve constructive interference depends on the amplitude and periodicity of the diffractive microstructure present, but according to experiments, if the first approximation is It shows that the thickness required to achieve a constructive increase in reflected light (ie λ / 2n) is satisfactory.

  In the region 18 </ b> C, the surface of the high refractive index layer 18 is in contact with the adhesive layer 21. The adhesive layer 21 typically has a refractive index lower than that of the high refractive index layer 18. Therefore, the reflected light at the boundary between the HRI layer 18 and the adhesive layer 21 destructively interferes with the same light reflection at the boundary between the lacquer layer 14 and the HRI layer 18, so that the metal 20 is present. There is an effect of suppressing the reproduction of an undesired hologram in a region other than the above.

  In FIG. 1B, metal platelet ink is applied to the individual areas 20A, 20B located in the OVD microstructure design 16A. FIG. 1C shows a cross-sectional view of FIG. 1B. In the example shown in FIG. 1B, the OVD microstructure 16A is recorded inside one metallic ink portion 20A rather than the OVD that exists throughout the device. In another embodiment, the OVD microstructure 24 and the metal ink 20A are substantially the same record, as shown in the plan view of FIG. 1D.

  One advantage of using printed metal ink compared to vacuum deposited metal layers is that it is possible to add colorant to the metal ink, for example, by using pigments or dyes. This is formed by printing a multicolor ink on which a reflective layer is recorded, thus enabling the generation of a multicolor hologram. Furthermore, the metal pieces or platelets in the ink can be varied from typical aluminum (silver effect), bronze (gold effect), iron, or zinc, giving different color effects.

  Colorant can be added to the embossing lacquer 14 and color can be added to the UV curable resin if a casting and curing process is used to form the holographic generating structure. Here, FIG. 2A shows a variation of the example of FIG. 1, where the metal ink layer 20 is printed to record as a row of multi-color metal inks 22 and 23, and the multi-color metal ink is a different color. Having inks 20, 22, and 23. From FIG. 2B it can be seen that the placement of the different metallic inks 22 and 23 is selected to be placed in the respective holographic images 24 and 25 generated by the surface relief microstructure. Thereby, the metal ink layer 20 forms a background. In the cross-sectional view where the holographic image 24 is arranged, the metallic color 22 is arranged in the OVD microstructure so as to form a non-holographic region, and the metallic color 23 is arranged in the holographic image 25. The device is coated with a layer of adhesive 21.

  2C and 2B are a plan view and a cross-sectional view of a color stripe DOVID having two different colored metal inks arranged in a DOVID artwork. The metal ink layer 20 and the metal color ink 22 are printed so as to be arranged in separate holographic images generated by the surface relief microstructures 24A-24C.

  Printing metal ink allows the ink to be placed on the embossed HRI coating 18. This facilitates alignment between the embossed pattern and the printed metal ink. This makes it possible to create a range of designs that can be multicolored as described above.

  The fact that the present invention solves the problem of poor reproduction of holograms based on metal inks so far means that the advantage of using printed metal inks is obtained. One important advantage is the alignment of the metal ink to the underlying embossed image, printing a security pattern like a filgre structure that has been reduced to 50 μm resolution with previous printing techniques Make it possible to do. A multicolor fillgreee structure is shown in FIG. FIG. 3A shows the metal layer 20 replaced by individual print areas of different color metal inks 61, 62.

  As can be seen from FIG. 3B, the ink 61 is printed in a fill-gree pattern surrounding the star shape defined by the ink 62. That is, the holographic image generated by the surface relief microstructure is divided into portions corresponding to a fill-gree pattern and a star shape.

  There are various methods by which these devices can be manufactured.

Method 1
1. The holographic pattern is embossed into an embossing lacquer or deformable carrier layer 12.

  2. An HRI layer 18 is vacuum deposited on the lacquer 12 for embossing.

  3. On the HRI layer 18, a platelet metal ink ink layer 20 is printed in the form of a pattern. This printing step can be performed by conventional printing processes including gravure printing, flexographic printing, lithographic printing and screen printing.

  In another embodiment, the third step of Method 1 may include aligning and printing a plurality of different colored metal inks (see FIG. 2).

  The HRI layer is typically zinc sulfide, but may be titanium dioxide or zirconium dioxide.

  A metal platelet ink similar to that described in WO2005 / 049745 can also be used. The metal platelet ink may have metal pigment particles and a binder. The metal pigment particles may have any suitable metal. One or more particles can be arbitrarily selected from the group including aluminum, stainless steel, nichrome, gold, silver, platinum and copper. Preferably, the particles have metal pieces.

  The metal ink layer may be opaque or translucent depending on whether the lower information is visible or not.

Method 2
This is similar to Method 1 except that Step 1 has been replaced by an in-situ resinized replication (ISPR) of cast and hardened or holographic structures. Technologies such as in-situ resinized replication (ISPR) have been developed so far where the resin is cast or cast on a profile that exhibits holographic or other optically variable effects. The resin is then retained on the substrate and the profile is retained by curing or removed from the profile mold. One example of this type of technique is UV casting. In a typical UV casting process, a flexible resin film is unwound from a reel and a UV curable polymer resin is coated onto the polymer film. If necessary, a drying stage removes the solution from the resin. The polymer film is held in intimate contact with a manufacturing device in the form of an embossing cylinder, and the optically variable structure on the manufacturing device is replicated in the resin held on the resin film. UV light is used to cure the resin at the contact area, and at the final stage, the mold and the film supporting the cured resin are rolled up again on the reel. Examples of this method are described in US Pat.

  Discontinued devices can be attached to an article or certificate in a variety of different ways, some of which are described below. The security device can be placed anywhere on the entire surface of the certificate, such as in the case of stripes or patches, but may be arranged in the form of a security thread that is only partially windowed on the surface of the certificate.

  Security threads, like certificates, passports, traveler checks, and other certificates, currently exist in many of the world's transits. In many cases, the threads are provided in a partially embossed or windowed form, where the threads appear as weaves in and out of the paper. One method of producing paper with so-called windowed threads can be found in EP0059056, EP0860298 and WO03095188, which describe different methods of embossing threads that are broadly exposed to a paper substrate. A wide thread, typically a thread having a width of 2-6 mm, is particularly useful and allows additional use of an optically variable device such as the present invention where the additional exposure portion is more suitable.

  The device is incorporated into the certificate so that the area of the device is visible from both sides of the certificate. As a technique, a conventional technique for forming a transparent region on both a paper and a polymer substrate is known. For example, WO8300659 describes a polymer banknote formed from a transparent substrate having an opacifying coating on both sides of the substrate. The opacifying coating is removed in certain areas on both sides of the substrate to form transparent areas. In one embodiment, the transparent substrate of the polymer banknote also forms the carrier substrate of the security device.

  In any case, the security device of the present invention can be incorporated into a polymer banknote so that it can only be seen from one of the substrates. In this case, the security device is attached to a transparent polymer substrate, and on one side of the substrate the opaque coating is removed so that the security device can be seen, but on the other side of the substrate the opaque coating is Attached on top of the security device to hide the security device.

  Methods for mounting the security device so that it is visible from both sides of the paper are described in EP1141480 and WO03054297. In the method described in EP1141480, one side of the device is fully exposed on one surface of a partially embedded certificate and partially exposed to a window on the other surface of the substrate.

  If striped or patched, the security device is formed on the carrier substrate and transferred to the security substrate in the next operational step. The device can be attached to a security substrate using an adhesive layer. The adhesive layer 15 is applied to the device or the surface of the security substrate to which the device is attached. After being transferred, the carrier substrate is removed and the security device is left as an exposed layer. In any case, the carrier layer can be left as part of a structure that functions as an outer protective layer.

  Following installation of the security device 10, a standard security printing process is performed in which the security board generates a security certificate, including wet or dry lithographic printing, intaglio printing, letterpress printing, flexographic printing, screen printing and / or One or all of the gravure printings are included.

Claims (29)

A transparent base layer having a surface provided with an optically variable relief microstructure; a transparent high refractive index layer adapted to the surface relief microstructure on the surface of the base layer; and the transparent high refractive index layer. A security device comprising a printed reflective metal layer,
The metal layer is printed in the form of a pattern;
The thickness of the transparent high refractive index layer is selected to achieve constructive interference of light at a wavelength λ in the range of 450 to 650 nm reflected from each surface of the transparent high refractive index layer. Feature security device.   The apparatus of claim 1, wherein the optically variable relief microstructure defines a diffraction grating or hologram.   The apparatus according to claim 1, wherein the base layer comprises lacquer or resin.   The apparatus of claim 1, wherein the optically variable relief microstructure is embossed on a surface of the base layer.   The apparatus of claim 1, wherein the optically variable relief microstructure is formed on a surface of the base layer by a casting / curing process. The device of claim 1, wherein the transparent high refractive index layer is formed from one of ZnS, TiO ₂ and ZrO ₂ .   The device according to any one of claims 1 to 6, wherein the thickness of the transparent high refractive index layer is about λ / 2n, where n is the refractive index of the transparent high refractive index layer.   The apparatus according to claim 1, wherein the wavelength λ is about 550 nm.   The device according to any one of claims 1 to 8, wherein a refractive index of the transparent high refractive index layer is in a range of 1.8 to 2.5.   The apparatus according to claim 1, wherein the metal layer is formed of metal particles such as a small piece or a platelet.   The apparatus of claim 10, wherein the metal particles are adapted to the surface relief microstructure.   12. Apparatus according to claim 10 or 11, wherein the metal particles comprise metal pieces or platelets with an average diameter of at least 1 [mu] m, preferably 5 [mu] m, more preferably 10 [mu] m.   The apparatus according to claim 10 or 11, wherein the metal particles have a thickness of 100 nm or less, preferably 15 to 100 nm, and more preferably 25 to 50 nm.   The apparatus according to claim 1, wherein the apparatus is formed of the different color inks.   15. An apparatus according to claim 14, wherein the metal particles have different colors.   The apparatus of claim 14 or 15, wherein the ink comprises different colorants.   The metal is aluminum, copper, zinc, nickel, chromium, gold, silver, platinum, or other metal, or one of related alloys such as copper-aluminum, copper-zinc or nickel-chromium. The device according to claim 1.   18. Apparatus according to any one of the preceding claims, wherein the metal layer is printed in the form of a pattern arranged in a pattern generated by the optically variable relief microstructure.   19. The apparatus according to any one of claims 1 to 18, wherein the pattern is a security pattern in the form of a greegly effect, for example, preferably having a minimum size of about 50 [mu] m.   A high-value article carrying the security device according to any one of claims 1 to 19.   From groups with banknotes, checks, traveler checks, certificates, revenue stamps, electronic payment cards (credit cards, debit cards, etc.), identification cards and certificates, driver's licenses, passports, brand protection or authentic labels, or stamps 21. The article of claim 20, which is a selected article. Providing a transparent base layer with a surface having an optically variable relief microstructure;
Providing a transparent high refractive index layer on the surface of the base layer to conform to the surface relief microstructure;
A method of manufacturing a security device, providing a reflective metal layer to the transparent high refractive index layer, wherein the metal layer is printed in the form of a pattern,
The thickness of the transparent high refractive index layer is selected to achieve constructive interference of light at a wavelength λ in the range of 450 to 650 nm reflected from each surface of the transparent high refractive index layer. Feature method.   23. The method of claim 22, wherein the printing comprises one of gravure, rotogravure, flexographic, lithographic, offset, letterpress, stencil and / or screen printing.   24. The method of claim 23, wherein the printing uses one or more inks comprising a binder and a metal platelet or piece.   The binder includes nitrocellulose, ethyl cellulose, cellulose acetate, cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), alcohol soluble propionate (ASP), vinyl chloride, vinyl acetate copolymer, vinyl acetate, vinyl, acrylic, 26. The method of claim 24, selected from the group comprising polyurethane, polyamide, ester gum, hydrocarbon, aldehyde, ketone, urethane, polyethylene terephthalate, terpene phenol, polyolefin, silicone, cellulose, polyamide, and ester gum resin.   26. The method of claim 25, wherein the binder comprises 50% nitrocellulose and 50% polyurethane.   27. A method according to any one of claims 22 to 26, wherein the optically variable relief microstructure is provided on the base layer surface by embossing.   27. A method according to any one of claims 22 to 26, wherein the optically variable relief microstructure is provided on the surface of the base layer by a casting / curing process.   30. A method according to any one of claims 22 to 28, wherein the security device according to any one of claims 1 to 19 is manufactured.

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